A Distributed Reactivity Model for Sorption by Soils and Sediments. 10. Relationships between Desorption, Hysteresis, and the Chemical Characteristics of Organic Domains

Abstract

Phenanthrene sorption and desorption equilibria were measured for 10 natural sorbents having significantly different geological ages and organic matter compositions. Three geologically young peats, one humic acid, three geologically old shales, and samples of kerogen isolated from each of the shales were examined. Elemental analyses and solid-state 13C-NMR spectra reveal that the oxygen/carbon (O/C) atomic ratios of the soil organic matter (SOM) as sociated with the samples decrease with increased age and, thus, apparently with diagenetic alteration. The sorption affinities of these materials for phenanthrene as well as their respective isotherm nonlinearities and hysteretic behaviors were found to correlate inversely with the O/C atomic ratio; samples containing more physically condensed and chemically reduced SOM matrices exhibited greater solute affinity, more nonlinear sorption equilibria, and more pronounced hysteresis. Observed relationships between the chemical and structural characteristics of associated organic matter and the sorption and desorption behaviors of the samples are captured effectively by the concepts underlying the Dual Reactive Domain Model advanced earlier in this series. This study thus extends that model to include the desorption process, supporting its general ap plicability for characterizing the overall behavior of soils and sediments with respect to solute uptake and release.

Aging effects on sorption–desorption behaviors of PAHs in different natural organic matters

“…Nevertheless, no correlation could be observed between the f rd and NOM aromaticity (p > 0.1) (aromaticity parameters of NOMs were listed in Table S3 in Supplementary material). The result is consistent with the observation of Huang et al that hysteretic behaviors of phenanthrene in geosorbents correlate inversely with the O/C atomic ratio and indicated that condensed samples exhibited greater solute affinity, and more pronounced hysteresis [34]. As the O/C atomic ratio of soil organic matter decreased with diagenetic alteration [16], it may represent important factor of geosorbent maturity.…”

Assessing desorption resistance of PAHs in dissolved humic substances by membrane-based passive samplers

“…The difference in the relative amount of oxygen-containing functional groups among HS samples was in agreement with previous studies that the oxygen/carbon (O/C) atomic ratios of natural organic matter decrease with increased age and, thus, apparently with diagenetic alteration [30]. The oxidation degree of HS appears to be significant in controlling reactivity with HOCs since a negative correlation was found between the log K OC values and the atomic O/C ratios of HS (Fig.…”

Veterinary antibiotic sorption to agroforestry buffer, grass buffer and cropland soils

“…To investigate the degree of hysteresis between OTC adsorption and extraction isotherms, an equation developed by Huang and Weber (1997) and modified by Zimmerman et al (2004) was employed. The hysteresis index (HI) was calculated as,…”